linux/Documentation/laptops/freefall.c

/* Disk protection for HP/DELL machines.
 *
 * Copyright 2008 Eric Piel
 * Copyright 2009 Pavel Machek <pavel@ucw.cz>
 * Copyright 2012 Sonal Santan
 * Copyright 2014 Pali Rohár <pali.rohar@gmail.com>
 *
 * GPLv2.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <string.h>
#include <stdint.h>
#include <errno.h>
#include <signal.h>
#include <sys/mman.h>
#include <sched.h>
#include <syslog.h>

static int noled;
static char unload_heads_path[64];
static char device_path[32];
static const char app_name[] = "FREE FALL";

static int set_unload_heads_path(char *device)
{
	if (strlen(device) <= 5 || strncmp(device, "/dev/", 5) != 0)
		return -EINVAL;
	strncpy(device_path, device, sizeof(device_path) - 1);

	snprintf(unload_heads_path, sizeof(unload_heads_path) - 1,
				"/sys/block/%s/device/unload_heads", device+5);
	return 0;
}

static int valid_disk(void)
{
	int fd = open(unload_heads_path, O_RDONLY);

	if (fd < 0) {
		perror(unload_heads_path);
		return 0;
	}

	close(fd);
	return 1;
}

static void write_int(char *path, int i)
{
	char buf[1024];
	int fd = open(path, O_RDWR);

	if (fd < 0) {
		perror("open");
		exit(1);
	}

	sprintf(buf, "%d", i);

	if (write(fd, buf, strlen(buf)) != strlen(buf)) {
		perror("write");
		exit(1);
	}

	close(fd);
}

static void set_led(int on)
{
	if (noled)
		return;
	write_int("/sys/class/leds/hp::hddprotect/brightness", on);
}

static void protect(int seconds)
{
	const char *str = (seconds == 0) ? "Unparked" : "Parked";

	write_int(unload_heads_path, seconds*1000);
	syslog(LOG_INFO, "%s %s disk head\n", str, device_path);
}

static int on_ac(void)
{
	/* /sys/class/power_supply/AC0/online */
	return 1;
}

static int lid_open(void)
{
	/* /proc/acpi/button/lid/LID/state */
	return 1;
}

static void ignore_me(int signum)
{
	protect(0);
	set_led(0);
}

int main(int argc, char **argv)
{
	int fd, ret;
	struct stat st;
	struct sched_param param;

	if (argc == 1)
		ret = set_unload_heads_path("/dev/sda");
	else if (argc == 2)
		ret = set_unload_heads_path(argv[1]);
	else
		ret = -EINVAL;

	if (ret || !valid_disk()) {
		fprintf(stderr, "usage: %s <device> (default: /dev/sda)\n",
				argv[0]);
		exit(1);
	}

	fd = open("/dev/freefall", O_RDONLY);
	if (fd < 0) {
		perror("/dev/freefall");
		return EXIT_FAILURE;
	}

	if (stat("/sys/class/leds/hp::hddprotect/brightness", &st))
		noled = 1;

	if (daemon(0, 0) != 0) {
		perror("daemon");
		return EXIT_FAILURE;
	}

	openlog(app_name, LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);

	param.sched_priority = sched_get_priority_max(SCHED_FIFO);
	sched_setscheduler(0, SCHED_FIFO, &param);
	mlockall(MCL_CURRENT|MCL_FUTURE);

	signal(SIGALRM, ignore_me);

	for (;;) {
		unsigned char count;

		ret = read(fd, &count, sizeof(count));
		alarm(0);
		if ((ret == -1) && (errno == EINTR)) {
			/* Alarm expired, time to unpark the heads */
			continue;
		}

		if (ret != sizeof(count)) {
			perror("read");
			break;
		}

		protect(21);
		set_led(1);
		if (1 || on_ac() || lid_open())
			alarm(2);
		else
			alarm(20);
	}

	closelog();
	close(fd);
	return EXIT_SUCCESS;
}